#include <iostream>
#include <chrono>
/**
* Adds a specified number of weeks to a given year_month_day date.
*
* @param ymd The base date as std::chrono::year_month_day.
* @param weeks The number of weeks to add (can also be negative to subtract).
* @return The resulting date as std::chrono::year_month_day.
*/
std::chrono::year_month_day add_weeks_to_date(std::chrono::year_month_day ymd, int weeks) {
// 1. Validate that the input date is a valid calendar date before doing math.
if (!ymd.ok()) {
throw std::invalid_argument("Invalid base date provided.");
}
// 2. Convert year_month_day to sys_days (a count of days since the epoch).
std::chrono::sys_days dp{ymd};
// 3. Add the weeks. std::chrono::weeks automatically scales to weeks * 7 days.
dp += std::chrono::weeks(weeks);
// 4. Convert back to year_month_day. This automatically recalculates
// the correct year, month, and day, handling all rollover logic safely.
return std::chrono::year_month_day{dp};
}
int main() {
// Initialize a sample date: November 8, 2026 using C++20 chrono syntax
std::chrono::year_month_day target_date = std::chrono::year(2026) / 11 / 8;
int weeks_to_add = 4;
try {
std::chrono::year_month_day result_date = add_weeks_to_date(target_date, weeks_to_add);
std::cout << "Original date: " << target_date << '\n';
std::cout << "After adding " << weeks_to_add << " weeks: " << result_date << '\n';
} catch (const std::exception& e) {
std::cerr << "Error: " << e.what() << '\n';
}
}
/*
run:
Original date: 2026-11-08
After adding 4 weeks: 2026-12-06
*/
